synchronization of digital output to analog output

Hello,

I´m trying to synchronize a digital output signal (in the end it should be a short TTL pulse) to an analog output. With this I want to tag the beam position change. I the already existing program there are the detector counters already synchronized (counter inputs) and this works, Adding in the same manner the digital output leads to the following error:

Error -200462 occurred at DAQmx Start Task.vi:4

Generation cannot be started, because the output buffer is empty.  

Before starting a buffered generation, write data. Unreserving a task empties the buffer. Changing the size of the buffer or setting the Regeneration Mode property will result in the buffer being unreserved and emptied. Changing the Sample Mode or configuring retriggering also empty the buffer.

I use an PCIe 6343 device with a Windows 7 32-bit computer.

What´s my error?

I attached the VI.

Thanks a lot!